The removal of obnoxious, odorous materials from gas streams, whether they are in industrial, commercial, or domestic environments, is a problem that is rapidly becoming more serious each year. Environmental control agencies are instigating increasingly stringent regulations to control objectionable emissions of all types, and at the same time a nation-wide energy crisis demands a reduction in the use of fuels for this purpose. Processes for the removal of pollutants from a gas stream utilizing incineration, adsorption, impingement, electrostatic attraction, centrifugation, sonic agglomeration, and ozonization are known. The most common of these processes in use at present appears to be incineration by direct flame or catalytic oxidation. Although these processes will remove particulates and organic vapors from a gas stream, they do so only with the expenditure of large amounts of energy and/or adsorbent material. Such processes may be non-continuous and therefore require interruption of the process, or they may employ oxidation catalysts subject to poisoning, and therefore are not entirely satisfactory.
U.S. Pat. No. 3,658,724 discloses an adsorbent catalyst for use in the removal of odorous and combustible components from the effluent gases of cooking and other processes by passing the effluent gases through a bed of the adsorbent catalyst and continuously or cyclicly oxidizing (by using a metallic oxidation catalyst known in the art which is incorporated in the adsorbent catalyst) the adsorbed components by increasing the temperature up to 300.degree. C.
U.S. Pat. No. 3,908,367 discloses a process for cleaning exhaust fumes from a combustion device by causing them to flow through a moving filter that is continually cleaned by air flowing through the filter in the direction opposite to the flow of exhaust fumes therethrough, and thence into the combustion device for reburning certain fume products captured by the filter. The filter useful in such a process captures mainly unburned carbon and metal particles and will not adsorb an appreciable amount of vapors, and even if it did adsorb vapors, there is no step of the process which would allow for desorption of the vapors so that these vapors could be subjected to reburning in the combustion device.
U.S. Pat. No. 3,930,803 discloses apparatus for purifying a gas stream of combustible vapors by passing the stream through an adsorption filter and charging the filter with combustible impurities to a predetermined level whereon, in a cyclic operation, the stream is interrupted and the filter is desorbed by passing a heated inert gas generated by stoichiometric burning of hydrocarbons through the filter, or the gas flow is switched from a saturated to a regenerated adsorption filter. The inert gas enriched with desorbate flows to a second burning chamber where air is added and the desorbate burned. Such a process is not continuous and does not provide for the removal and disposal of combustible particulate material in a gas stream.
Assignee's copending patent application, U.S. patent applicaton Ser. No. 21,997, filed Mar. 19, 1979, in the names of C. Davis, G. Foss, and T. Shevlin, discloses a system for the removal of particulate material from an air stream in a continuous, energy-efficient process. The improved collector of the present invention provides for the removal of organic vapors as well as particulate matter from a gas stream and affords the removal of at least 85%, and preferably at least 95%, of the total organic content of an air stream.
The superior energy efficiency of the collector of the present invention results from the use of much thinner adsorbent beds than is used in prior art apparatus. These thinner beds require much less energy for their regeneration. In addition, the concentration of organic vapors realized by use of the collector of the present invention makes possible a reduced energy requirement for the processing of this concentrated stream.